I love 17hmr. great round. super flat shooting and very accurate within its intended range. the p-dogs I've gotten with it pretty much explode. accurate enough for paint balls at 100 yards. its a a whole different thing from .22lr, and past 100 yards it out does the 22mag.
one of the good things about it, its very frangible, so misses and pass threw's don't have nearly as much chance of a dangerous ricochet.
don't have any experiance with the .243. seems like a pretty good round.. though maybe a bit of over kill for rodents